The disclosures of the Japanese Applications Nos. 2000-008572, 2000-010963, 2000-175774 and 2000-387282, are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid-crystal display device making use of a polymer-dispersed liquid crystal.
2. Related Background Art
In liquid-crystal display devices which make use of polymer-dispersed liquid crystal to perform efficient action, usually the display is made utilizing two states that the liquid crystal is brought into a non-transparent state (made to stand non-transparent: light scattering state) by non-electrification and is brought into a transparent state (made to stand transparent: light non-scattering state) by electrification. Stated specifically, in the liquid-crystal display devices of such a type, a polymer-dispersed liquid crystal is so disposed as to be held between opposing transparent electrodes. Upon application of in-phase alternating-current signals to both the transparent electrodes, the liquid crystal comes into a light scattering state where no voltage is applied, and, upon application of out-of-phase alternating-current signals to both the transparent electrodes, it comes into a transparent state where a voltage is applied. The driving of liquid crystal in this way brings patterns into the transparent state and their surroundings into the light scattering state, whereby transparent regions can be displayed on a white background similar to ground glass; or brings patterns into the light scattering state and their surroundings into the transparent state, whereby white regions can be displayed on a transparent background.
Where transparent regions are displayed on a white background, any particular problem does not arise even in apparatus constructed as described above. However, where it is attempted to display white regions on a transparent background, the following problems may arise.
Think about display regions set like islands in a transparent background. In such a case, even when the background region which surrounds display regions is kept into a transparent background by applying a voltage thereto, wiring areas extending to the display regions come into question. More specifically, where the island-like display regions stand non-electrified, i.e., the voltages applied to the both electrodes are in phase, the wiring areas extending to those regions have of course the same phase as the opposing transparent electrodes. This means that, when the island-like display regions are displayed in the light scattering state, the wiring areas extending there to the display regions also come into the light scattering state and are inevitably simultaneously displayed.
In liquid-crystal display devices, the fact that the island-like display regions are displayed in the background standing transparent means that, when a liquid-crystal display panel is incorporated in an optical system, display marks are so displayed as to come up to the surface as white regions in a state what is called xe2x80x9csuperimposedxe2x80x9d to image formed by light beam transmitted through a transparent region. In such a case, to the display mark, wiring through which a voltage is supplied thereto is connected, and hence the voltage is applied to the liquid crystal via the wiring, so that all the segments that constitute the display mark look like as if strings are attached corresponding to the wiring areas extending from the margin of a picture, to spoil the light beam image transmitted through the transparent region.
In addition, at the boundary between a background area and a display mark, there is a boundary between the segments that constitute the transparent electrodes corresponding to the both, and this boundary remains inevitably as a blank area where no electrode pattern is present. In this blank area, no electric field comes up to the liquid-crystal region present opposingly to this blank area, and hence the light scattering state is always maintained. Namely, what is to be displayed when the background area is made transparent and the display mark is also made transparent is displayed as a white region as if the blank area is an edging of the display mark. When the display mark area is made white, a display mark is formed in which both the blank area and the display mark area are painted out as a white region.
Thus, in conventional liquid-crystal display devices, the display mark can not completely be made to disappear even when it is unnecessary, and there comes to be a disadvantage on display that the wiring area goes on and off concurrently every time the display mark goes on and off. Such a disadvantage provides a great obstacle when any desired display is optically superimposed on a background image. That is, the display to be superimposed is desired not only to be simply displayed, but also to disappear completely when it is unnecessary.
As for the polymer-dispersed liquid crystal, it responds more slowly as temperature is lower, and hence may cause a problem that the brightening of display segments does not agree with the timing of illumination as long as the illumination is merely performed.
For example, at a normal temperature of 25xc2x0 C., the polymer-dispersed liquid crystal takes about 10 msec as a time taken to change from the light scattering state to the transparent state and about 60 msec as a time taken to change from the transparent state to the light scattering state, changing almost instantaneously. However, at a low temperature of xe2x88x9210xc2x0 C., it takes about 300 msec as a time taken to change from the light scattering state to the transparent state and about 1,400 msec as a time taken to change from the transparent state to the light scattering state, showing a very slow response.
Hence, where one of a plurality of segments is selected by a selector, the liquid crystal responds so slowly at low temperature that the illumination may end before the selected segment changes into the light scattering state, and further that a segment having been selected before that is illuminated. Thus, there is a problem that any selected segment is not accurately illuminated. This problem has not been solved under existing circumstances.
Accordingly, an object of the present invention is to provide, as first invention of the present application, a liquid-crystal display device that enables any desired display to be superimposed on the background image while preventing the difficulty that the wiring area extending to a display mark is displayed or only the edging of the display mark is displayed.
To achieve the above object, the liquid-crystal display device of the first invention comprises a polymer-dispersed liquid-crystal layer capable of coming into a light scattering state when no voltage is applied, and first and second transparent electrodes capable of forming an electric field in the polymer-dispersed liquid-crystal layer;
the first transparent electrode having a first electrode pattern and a second electrode pattern disposed adjoiningly to the first electrode pattern via a boundary area between them;
the boundary area having a width adequate to make transparent the polymer-dispersed liquid-crystal layer at its area corresponding to the boundary area, by the action of an electric field formed by the second electrode pattern and second transparent electrode.
According to the first invention, when in the above device the first electrode pattern and the second electrode pattern come into the transparent state upon application of a voltage to the both, the surrounding electric field strays into the polymer-dispersed liquid-crystal layer lying in a region opposing to the boundary area of the both patterns, so that the boundary area of the both patterns is not displayed and not seen.
In the liquid-crystal display device of the first invention, preferably the first electrode pattern may be a display pattern, the second electrode pattern may be a background pattern, and boundary area may have a width substantially equal to the layer thickness of the polymer-dispersed liquid crystal layer.
In the liquid-crystal display device of the first invention, also preferably the first electrode pattern may be a wiring pattern, the second electrode pattern may be a background pattern, and the first electrode pattern and the boundary area may have a total width substantially equal to the layer thickness of the polymer-dispersed liquid crystal layer.
An object of a second invention of the present application is to provide, a liquid-crystal display illumination device that enables appropriate illumination of the selected segment even when there are changes in temperature.
The second invention provides a liquid-crystal display illumination device comprising;
a display panel having a plurality of display segments having sealed a polymer-dispersed liquid-crystal layer capable of switching a light scattering state where light is scattered and a transparent state light non-scattering state where light is transmitted;
a selection part which selects at least one display segment of the plurality of display segments of the display panel;
a drive circuit which brings into the light scattering state the display segment selected by the selection part and drives an unselected region in the transparent state;
an illumination part which illuminates the display panel;
a temperature detection part which detects the temperature of the polymer-dispersed liquid-crystal layer or its vicinity; and
an illumination control part which controls delay time and/or light-emission time in accordance the temperature detected by the temperature detection part; the former being the time after the selection part has been operated and until the illumination part starts illumination, and the latter being the time after the illumination part has started illumination and until it ends the illumination.
In the liquid-crystal display illumination device of the second invention, preferably the delay time in the illumination control part may be set longer than the time for which the display segment of the display panel at the detected temperature switches from the light scattering state to the transparent state.
In the liquid-crystal display illumination device of the second invention, also preferably the delay time in the illumination control part may be set shorter than the time for which the display segment of the display panel at the detected temperature switches from the transparent state to the light scattering state.
In the liquid-crystal display illumination device of the second invention, still also preferably the light-emission time in the illumination control part may be set equal to or longer than the time for which the display segment of the display panel switches from the transparent state to the light scattering state.
In the liquid-crystal display illumination device of the second invention, still also preferably the device may further comprise;
a photometric part which measures the brightness of the display panel or its vicinity; and
a light emission inhibition part which inhibits the illumination part from emitting light when the photometric value measured by the photometric part is higher than a preset luminance.
In the liquid-crystal display illumination device of the second invention, still also preferably the illumination part may comprise a light source which generates light and a light guide member which guides to the display panel the light emitted from the light source.
The polymer-dispersed liquid crystal may also be used in a view finder of a camera.
In the liquid-crystal display device making use of this polymer-dispersed liquid crystal, the liquid-crystal layer can be switched into two modes of light non-scattering state/light scattering state by switching a voltage applied to the liquid-crystal layer, and any desired information can be displayed by making the shape of the electrode (transparent electrode) have any desired shape (construct the display panel).
Accordingly, the liquid-crystal display device thus constructed may be disposed in the vicinity of a screen in the view finder of a camera so that any optical image formed on the screen can be recognized through the liquid-crystal display device. In this state, the voltage applied to the liquid-crystal layer may be controlled, whereby any desired information can appropriately be displayed superimposingly on the optical image formed on the screen.
In such a case, the liquid-crystal display panel of the liquid-crystal display device may consist basically of two sheets of transparent substrates provided with a plurality of transparent electrodes and a polymer-dispersed liquid-crystal layer sealed between the two sheets of transparent substrates, and the transparent electrodes having the desired shapes and opposing each other, interposing this polymer-dispersed liquid-crystal layer may constitute the display segment. Then, the polymer-dispersed liquid-crystal layer held between the transparent electrodes to which a voltage has been applied does not scatter light (light non-scattering state) and only the polymer-dispersed liquid-crystal layer to which a voltage has not been applied scatters light (light scattering state).
Thus, the display segment can be displayed on the liquid-crystal display panel in any desired form by selectively applying the voltage to a plurality of transparent electrodes constituting a plurality of display segments disposed in the liquid-crystal display panel.
In view finder devices of electronic optical instruments such as single-lens reflex cameras, there is a demand that, when a plurality of display segments provided in a view finder are selected in order to show their use conditions and so forth, the selected display segments are desired to be displayed in a state contrasting distinctively with other display segments so that these are visually clearly recognizable by a photographer.
For example, in a single-lens reflex camera so constructed that one focus area is selected from a plurality of focus areas to perform focusing, the information on what focus area stands selected at the time of photo-taking is one of those which are desired to be clearly recognized by a photographer through a display segment corresponding to the selected focus area (hereinafter often xe2x80x9cindication segmentxe2x80x9d).
A third invention of the present application was also made taking account of such circumstances, and has its object to provide a liquid-crystal display device that enables the indication segment (a specific display segment selected by a photographer from among a plurality of display segments) to be clearly recognized in a state contrasting distinctively with other display segments.
The third invention provides a liquid-crystal display device comprising;
a liquid-crystal display panel having an indication segment comprising a plurality of indications capable of making selective display by selection operation, and a display segment comprising an indication other than the former indications;
a light source;
a light guide means for guiding to the liquid-crystal display panel the light emitted from the light source;
selection means for performing the selection operation;
control means for controlling the display segment and the indication segment selected by the selection operation, into a light scattering state or a light non-scattering state; and
an action-detecting means for detecting the state of action of an electronic optical instrument in which the liquid-crystal display panel is incorporated;
the control means being capable of forcedly controlling into the light non-scattering state the display segment having come into the light scattering state, to make the light source emit light, at the time the action-detecting means has detected, as the state of action, a state of action which requires to make sure of the selected indication. This enables the indication segment to be clearly recognized in a state contrasting distinctively with other display segments, even in an instance in which any other segment stands provisionally selected when a specific segment is selected.
In the liquid-crystal display device of the third invention, the control means may preferably be so made up that it makes the light source emit light for a given period and, after lapse of the given period, makes return into the light scattering state the display segment forcedly changed into the light non-scattering state. This enables the indication segment to be clearly recognized by a photographer in a state contrasting distinctively for a given period, and thereafter enables another display segment to be recognized by the photographer.
The liquid-crystal display device of the third invention may also comprise photometric means for measuring the luminance of the liquid-crystal display panel or its vicinity, connected to the control means;
the control means being capable of inhibiting the light source from emitting light when the luminance measured by the photometric means is higher than a preset value. This enables the selected indication segment to be illuminated by the light from the light source to become visually recognizable with ease when the environment around the liquid-crystal display panel is dark, and enables the selected indication segment to be brought into the light scattering state to look dark to become visually recognizable with ease when the environment around the liquid-crystal display panel is bright.
In the liquid-crystal display device of the third invention, the electronic optical instrument may be an autofocus camera having a plurality of focus areas, where the state of action which requires to make sure of the selected indication is at least one of an autofocusing state and a focus-area-selected state. This makes it possible, in the state of autofocusing action, to make sure of the focus area standing selected by the indication segment, and makes it easy, in the focus-area-selected state, to select a new focus area while making sure of the focus area standing already selected.